Mobile gantry crane having a resiliently supported bridge



Aprili 1966 D. E. HOLT ET AL. 3247,95

MOBILE GANTRY CRANE HAVING A RESILIENTLY SUPPORTED BRIDGE Filed 06%,. 28, 1964 3 Sheets-Sheet l mm 1 :1: WW

INVENTORSQ a. L. HOLT A. 1 was y KG. WINTER Affamvey April 26, 1966 o. E. HOLT ET AL 3,247,975

MOBILE GANTRY CRANE HAVING A RESILIENTLY SUPPORTED BRIDGE Filed Oct. 28. 1964 3 Sheets-Sheet 2 INVENTORS D. E HOLT A- v KORE BY KG. WINTER AfKaPuEY April 26, 1966 D. E. HOLT ET AL. 3,247,975

MOBILE GANTRY CRANE HAVING A RESILIENTLY SUPPORTED BRIDGE 3 Sheets-Sheet 5 Filed 00*.

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HOLT V. KORE BY 6. WINTER Affonwe'y United States Patent Ofitice 3,247,975 Patented Apr. 26, 1966 Kenneth G. Winter, Miiwaukee, Wis., assignors to Harnischfeger Corporation, Miiwaukee, Wis, a corporation of Wisconsin Filed Oct. 28, 1964, Ser- No. 407,193 6 Claims. (Cl. 212-43) The present invention relates generally to mobile lifts commonly referred to as traveling gantry cranes, and more particularly to a crane of this type which is adapted to travel over and conform to uneven terrain without causing twisting of the bridge or undue strain in any of the parts. The invention finds particular utility in a rubher mounted, A-frame type gantry crane.

Cranes of this general type have been heretofore proposed and used with a certain amount of success. For example, the crane shown in the US. Patent No. 3,059,- 782 issued on October 23, 1962, and entitled Mobile Lift, provided for pivotal movement between one of the side A frames and the bridge which resulted in flexibility in the crane and the accommodation of undulating terrain without a twisting strain being imposed on the bridge. The other side A frame was rigidly fastened to the bridge to thereby provide stability to the bridge and to prevent uncontrolled twisting which would otherwise occur if both side frames were pivoted to the bridge. This crane had shortcomings, however, because it was not sufficiently flexible nor did it eliminate stress under all operating conditions.

In accordance with the present invention, a mobile gantry crane has been provided wherein the said frames are each attached to the bridge in a novel manner to provide the flexibility necessary to accommodate uneven terrain, regardless of the direction of travel of the gantry crane. More specifically, the side frames are each pivotally attached to the bridge along an axis which is generally parallel to the length of the bridge and in such a manner thatonly limited pivotal action between the bridge and side frames can occur. Furthermore, resilient and preferable pre-loaded means are provided between the side frames and the bridge for resiliently preventing undue or excessive movement therebetween.

Another aspect of the invention relates to an improved gantry crane of the above type wherein the ground supporting wheels are steerable and permit movement of the crane in any direction. Thus, even when the crane travels in a direction parallel with the bridge, the side frames are nevertheless capable of limited pivot-a1 movement relative to the bridge, thereby preventing undue stress in or twisting of the bridge. That is to say, when uneven ground is encountered which would cause one side frame to tilt in one direction and the other frame to tilt in the opposite direction, each frame can pivot relative to the beam, thereby preventing the beam from torsionally twisting, i.e., twisting from one of its ends to the other. Thus the load on the beam continues to hang in a vertical direction under the influence of gravity without applying a twisting motion to the beam. The beam remains normal to the load. In other words, by means of the present improved mounting means between the side frames and the bridge, undulating ground can be accommodated without bridge twisting regardless of the direction of travel of the crane.

A more specific object of the invention relates to a gantry crane of the above type in which the mounting means includes resilient means between the side frames and the bridge, more specifically this means includes a series of Belleville springs. The invention contemplates that the Belleville springs can be pre-loaded so that when the crane is operating on level ground, the bridge is effectively cushioned or resiliently mount-ed, and flexibility of the bridge is assured without the bridge being unstable.

These and other objects and advantages of the present invention will appear hereinafter as this disclosure progresses, reference being had to the accompanying drawings in which:

FIGURE 1 is a side elevational view of a gantry crane embodying the present invention;

FIGURE 2 is a front elevation of the crane shown in FIGURE 1;

FIGURE 3 is an enlarged, fragmentary view of a portion of the crane shown in FIGURE 1;

FIGURE -4 is a fragmentary and enlarged view of a portion of the device shown in FIGURE 3 but showing the Belleville springs in the fully compressed position.

FIGURE 5 is a fragmentary and elevational view of the upper portion of the crane shown in FIGURE 1 but on an enlarged scale;

FIGURE 6 is an enlarged cross sectional View taken along the line 6-6 in FIGURE 5.

Referring in greater detail to the drawings, the side frames S1 and S2 are substantially identical, for purposes of this invention, and a detailed reference will be made to one with the understanding that corresponding parts can be found in the opposite side.

The side frames in general are of an A-shaped configuration and have ground engaging wheel assemblies W1 and W2 spaced along their lowersides. These wheel assemblies W1 and W2 include a rubber tired wheel 3 and 4, respectively, which are mounted in bifurcated end portions 6 and 7 of the vertical steering spindles 8 and 9. These spindles are suitably journalled in bearings 10 in the side frame to permit rotation and consequent steering of each of these wheels and thereby provide any direction of travel for the crane. The wheels are driven by an individual power plant 12 carried by each spindle.

The side frame includes upwardly converging I-beam members 13 and 14, and a lower structural steel member 15 which rigidly connects the lower ends of the members 13- and 14 by suitable gusset plates 16 and 17. A cross brace 18 connects the intermediateportions of the members 13 and 14 and the upper end of the converging members are rigidly secured together by a pair of suitable gusset plates 20 and 21. The upper end of each member 13 and 14 has a cross member 13a. and 14a welded thereto.

An elongated bridge B spans across the distance between the spaced apart side frames and is pivotally connected at each of its ends to the side frames about an axis which is generally parallel to the bridge so that the side frames can each pivot individually and independently relative to the bridge and to each other. More specifically, each end of the bridge has a generally U-shaped member 25 which extends downwardly from the bridge main member 26 and is rigidly secured thereto as by welding. This U-shaped member includes oppositely inclined portions 27, 28 and a large tubular journal member 29 is positioned between these portions. Portions 27 and 28 lie closely adjacent, respectively, the cross members 13a and 14a.

The U-shaped member is positioned between its corresponding gusset plates 20 and 21 and a pivot shaft 30 extends through the journal member29 and its ends are journalled in the gusset plates 20, 21. In this manner a rather long pivot axis is provided between the side frames and the bridge which offers considerable rigidity against transverse movement of the side frames relative to and in a direction parallel to the elongated bridge. This pivotal connection permits swinging of the side frames in 21 normal direction relative to the length of the bridge, which swinging movement is limited by means new to be described.

At each of the upper ends of the side frame members 13 and 14 and more particularly located in the cross members 13a, 14a, thereof, is a resilient means R which acts to resiliently maintain the normal position between the side frames and the bridge. More specifically, this resilient means includes a series of Belleville spring washers 40 which are stacked as shown in the drawings around a large bolt 41 that extends through the cross members 13a, 14a. A nut 42 holds the bolt captive and thus the nut and bolt can be adjusted to provide for pre-loading of the Belleville springs between the pair of shims 43, 44 which are also mounted on the bolt 41.

As can be seen clearly in FIGURE 3, the bolt 41 is adapted to bear against the member 27 of the bridge and the arrangement shown in FIGURE 3 is the normal condition wherein the crane is on level ground. Under these circumstances, the bridge is not twisted and all of the resilient mounting means R are in the position as shown and these springs are preferably pre-loaded to about 25 percent of their total capacity. In other words, if each of the spring assemblies R can absorb 5,000 pounds of thrust, the nut is tightened on the bolt so as to compress the springs to about 25 percent of this load, that is, the spring assemblies are pre-loaded to about 1250 pounds.

With the above arrangement the bridge is cushioned and resiliently held in its normal position by the four resilient mounting means, one of which is located at the top end of each of the inclined members 13 and 14 of each of the side frames S1 and S2.

This resilient mounting means and the pivotal connections between the side members and the bridge permit the crane to travel over uneven terrain without any undue strain being imposed on the parts. This flexibility however, is limited by the resilient mounting means so that the bridge has stability for proper operation of the winches W and other equipment which are operative therefrom.

As shown in the broken lines in FIGURE 3, when one of the side frames has been rotated relative to the bridge in the order of approximately 2 /2 degrees, the resilient mounting means would be compressed to the extent indicated by the broken lines.

It is important to provide for pivotal movement between each of the side frames and the bridge so that no binding or undue strains occur therebetween, particularly when the crane is traveling in a direction generally paral lel to the length of the bridge.

By means of the present invention, therefore, the improved gantry crane can be operated over uneven ground in any direction and while flexibility has been provided between each of the side frames and the bridge, nevertheless the bridge is not unstable and the entire unit is highly efficient in performing the functions for which it was designed.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the Subject matter which is regarded as the invention:

I claim:

1. A mobile gantry crane comprising a pair of spaced apart side frames each having ground engaging wheels, an

elongated overhead bridge extending between said frames, a pivotal connection between each of the side frames and the overhead bridge for relative movement about an axis generally parallel to said bridge, and resilient means connected between the side frames and the bridge for limiting said pivotal movement therebetween and for resiliently stabilizing said bridge against pivoting relative to said side frames.

2. A crane as defined in claim 1 further characterized in that said wheels are steerable and the crane can travel in a direction parallel to said elongated bridge, and each of said side frames can pivot relative to said bridge within predetermined limits during said travel.

3. A crane as defined in claim 1 further characterized in that said resilient means includes Belleville springs, and including means for preloading said springs whereby they resiliently stabilize said bridge.

4. A mobile gantry crane comprising a pair of spaced apart side frames each having steerable ground engaging wheels to permit travel of said crane in any direction over the ground, an elongated overhead bridge extending between said frames, a pivotal connection between each of the side frames and the overhead bridge, for relative movement about an axis generally parallel to said bridge, and resilient means including Belleville springs connected between each side of each of the side frames and the bridge for limiting said pivotal movement therebetween and for resiliently stabilizing said bridge against pivoting relative to said side frames.

5. The crane as set forth in claim 4 further characterized in that said resilient means also includes an adjustable bolt means on which said Belleville springs are mounted and can be compressed for pre-loading.

6. A mobile gantry crane comprising a pair of spaced apart side frames each having ground engaging wheels, an elongated overhead bridge extending between said frames, a pivotal connection between each of the side frames and the overhead bridge for relative movement about an axis generally parallel to said bridge, and bolt means between each side frame and each side of the bridge, and a series of Belleville springs on each bolt means, said bolt means and springs bearing between said side frames and said bridge and resiliently limiting pivotal movement therebetween.

References Cited by the Examiner UNITED STATES PATENTS 1,884,981 10/1932 Otto 2671 X 3,059,782 10/1962 Baudhuin 21213 3,128,071 4/1964 Frazier-Nash 267-1 X FOREIGN PATENTS 1,013,535 4/1952 France. 1,126,092 3/ 1962 Germany. 1,128,958 5/1962 Germany.

HUGO O. SCHULZ, Primary Examiner.

SAMUEL F. COLEMAN, A. L, LEVINE, Examiners. 

1. A MOBILE GANTRY CRANE COMPRISING A PAIR OF SPACED APART SIDE FRAMES EACH HAVING GROUND ENGAGING WHEELS, AN ELONGATED OVERHEAD BRIDGE EXTENDING BETWEEN SAID FRAMES, A PIVOTAL CONNECTION BETWEEN EACH OF THE SIDE FRAMES AND THE OVERHEAD BRIDGE FOR RELATIVE MOVEMENT ABOUT AND AXIS GENERALLY PARALLEL TO SAID BRIDGE, AND RESILIENT MEANS CONNECTED BETWEEN THE SIDE FRAMES AND THE BRIDGE FOR LIMITING SAID PIVOTAL MOVEMENT THEREBETWEEN AND FOR RESILIENTLY STABILIZING SAID BRIDGE AGAINST PIVOTING RELATIVE TO SAID SIDE FRAMES. 